1. Field of the Invention
The present invention relates to headlamps for vehicles, and particularly relates to a headlamp for a vehicle, being capable of improving luminous flux efficiency to a light source and performance of the lamp, and also capable of providing an original design for appearance of the headlamp which has not been existed. Furthermore, the present invention relates to a headlamp for a vehicle, being capable of changing luminous intensity distribution properties for driving and for passing-by (or so-called xe2x80x9chigh-beamxe2x80x9d and xe2x80x9clow-beamxe2x80x9d) by utilizing a single light source.
2. Detailed Description of the Prior Art
FIGS. 1 to 3 show constructions of conventional a headlamp for a vehicle. Lamp 90 shown in FIG. 1 is composed of a light source 91, a revolved parabolic reflector 92 in which the light source 91 is positioned at its focal point, and a lens 93 having lens cuts 93a provided thereon. Light emitted from the light source 91 is reflected by the above mentioned revolved parabolic reflector 92 so as to become parallel with reference to the optical axis of the light source. The reflected light is diffused appropriately by the lens cuts 93a to obtain a required luminous intensity distribution property.
Moreover, lamp 80 shown in FIG. 2 is composed of a light source 81, a composite reflector 82, and a lens 83. The composite reflector 82 is composed of a plurality of parabolic columnar reflectors in which a parabola appears in a horizontal cross section when the lamp 80 is installed. Incidentally, the light source 81 is arranged at the focal point of the parabola. Further, the lens 83 is not provided with any lens cut formed thereon and is plain. In this lamp 80, a luminous intensity distribution property thereof can be adjusted by the above-mentioned composite reflector 82 itself. Furthermore, lamp 70 shown in FIG. 3 is composed of a light source 71, an elliptic type reflector 72, an aspheric lens 73, and a shade 74 if required. The elliptic type reflector 72 has a first focal point f1 where the light source 71 is positioned and is composed of elements such as revolved ellipsoidal reflector, composite ellipsoidal surface, ellipsoidal free curved surface or the like. In this case, the major axis of the elliptic type reflector 72 coincides with the illuminating direction and a light source image is generated by focusing it at the second focal point f2 thereof. Illuminating light can be obtained by enlarging and projecting the light source image by the aspheric lens 73. A desired luminous intensity distribution property can be obtained by shielding an unnecessary portion of light by means of the shade 74 (in the shown conventional example, the lower half of luminous flux converging at the second focal point f2 is shielded). Incidentally, the lamp system employing this type of elliptic type reflector 72 is called a projector type lamp.
However, out of the above-mentioned prior art lamps, for the lamp 90 shown in FIG. 1 the lens cuts 93a need to have a large optical power. As a result, the change in thickness of the lens 93 becomes large, which deteriorates transparency thereof. Accordingly, there are problems in that it is impossible to provide a suitable lamp appearance having transparency and a preferable depth to which consumers prefer in the market.
Furthermore, in the lamp 80 shown in FIG. 2, since the lens 83 is plain with no lens cut provided thereon, a suitable lamp appearance having a superior transparency can be obtained. However, it is difficult to ensure a luminous intensity distribution property in a width direction because the luminous intensity distribution property is formed by the composite reflector 82 positioned relatively deep. As a result, there is a problem in that formation of luminous intensity distribution property is limited.
Further, it is difficult to install the lamp 70 shown in FIG. 3 because of its depth. In addition, the illuminating area is small due to the small diameter of the employed aspheric lens 73. When the lamp 70 is employed as a headlamp, visibility thereof from opposed vehicles may be deteriorated.
In addition to the above-mentioned problems, since the lamps 90, 80, 70 having the above-mentioned prior art construction are widely employed, it is difficult to discriminate between these lamps and the other ones and also obtain an original design. Furthermore, each luminous flux efficiency of the lamps 90, 80, 70 having the above-mentioned prior art configurations is affected in response to the area of the reflector. Thus, when the lamp is reduced in its dimension (for example, making it thinner in width or both vertical and horizontal dimensions be made smaller) due to the demand in the market, the brightness thereof becomes significantly lower.
Besides, cross-sectional shape of luminous flux in the lamp 70 shown in FIG. 3 near the shade 74 is a semicircular shape (lower half of circle). When the luminous flux having such the shape is projected toward the illuminating direction by the projector lens 73 having a focal point f3 near the shade 74, the luminous flux is made inverted and emitted to have an upper half of circle shape toward the illuminating direction. Thus, a luminous intensity distribution shape suitable for passing-by can be obtained because the projected light does not contain any upward light which is the cause of dazzling light for opposed vehicles. However, in actual operation, in order to readily recognize walkers passing by or road signs, a shade 74 is modified to generate an appropriate light in the upper left-side direction for left-side traffic.
In this lamp 70, however, almost half of the reflected light from the elliptic type reflector 72 is shielded by the shade 74 as clearly shown in the above-described explanation, as a result the luminous flux efficiency to the light source 71 is lowered and there is another problem in that the lamp 70 is relatively darker for energy consumption.
Moreover, it has been proposed that with this type of a projector headlamp 70 provided is a luminous intensity distribution switching means for changing luminous intensity distribution properties for driving and for passing-by by retreating, for example, a shade 74 from the luminous flux of the light reflected from the elliptic type reflector 72. In this case, however, any control for the shape of the luminous intensity distribution property is not substantially carried out and there is still another problem in that any luminous intensity distribution property for practical use can not be obtained.
An object of the present invention is to provide a headlamp for a vehicle being capable of improving luminous flux efficiency to a light source and increasing its brightness further even when the same light source is used. Another object of the present invention is to provide a headlamp for a vehicle being capable of providing an original design for appearance of the headlamp which has not been existed without decreasing the luminous intensity even when the height thereof is decreased.
In order to achieve the above-mentioned objects, the present invention provides a headlamp for a vehicle, comprising a light source; a first reflector formed of a parabolic reflector and having a focal point at which the light source is positioned; a light guide passage for guiding light to the backside of the first reflector, provided at an appropriate position thereof; a second reflector formed of a parabolic reflector and provided outside thereof corresponding to the light guide passage of the first reflector; a third reflector provided in the vicinity of an optical axis of the first reflector for converging and transmitting a light from the light source to the vicinity of the light guide passage; and a lens provided in front of the first and second reflectors in an illuminating direction.
According to the headlamp for a vehicle of the present invention, light which is not captured by the first reflector and which has not been utilized in the prior art can be collected and utilized by the third reflector, thereby being capable of illuminating it in the illuminating direction by the second reflector via the light guide passage. As a result, there is provided a headlamp for a vehicle being capable of improving luminous flux efficiency to a light source and increasing its brightness further even when the same light source is used and also improving performance of the lamp.
In the design aspect, even when, for example, the height of the first reflector is decreased so that the captured quantity of luminous flux by the first reflector is decreased, the decreased quantity of luminous flux can be collected by the third reflector and utilized by the second reflector as a illuminating light. Accordingly, it is possible to provide an original design having a lens height of about 30 mm which has not been able to be obtained according to the prior art without deteriorating any performances as a headlamp. Thus, a superior effect to improve commercial value can be provided.
In the present invention, a focal point of the above-mentioned second reflector may be set in the vicinity of the light guide passage.
Further, the third reflector may be an elliptic type reflector having a first focal point at which the light source is positioned and a second focal point in the vicinity of which an inlet of the light guide passage is positioned.
In addition, the third reflector may serve as a hood for the light source.
Furthermore, an optical axis of the second reflector is almost parallel to the optical axis of the first reflector on at least one cross section in either horizontal direction or vertical direction.
Further, it is preferred that the optical axis of the second reflector may be set by about 2xc2x0 downward relative to the optical axis of the first reflector.
Besides, the light guide passage may be provided above a horizontal line which passes through the light source and which is perpendicular to the optical axis and at a range of xc2x145xc2x0 around the light source as the origin in a forward and backward direction relative to the horizontal line on the basis of the installation state of the headlamp for a vehicle.
Further, the light guide passage may have an inlet and an outlet which are appropriately spaced and may be tubular.
In addition, in the present invention, at least a part of the outlet of the light guide passage may contain a plane perpendicular to a straight line which is perpendicular to the optical axis of the second reflector.
Furthermore, the shape of the outlet of the light guide passage may be adjusted to be suitable to form a luminous intensity distribution property required for the second reflector.
Besides, an upper end of the light guide passage may coincide with at least one of an upper end of the first reflector and an upper end of the second reflector.
Furthermore, an upper end of the effective area of the lens may coincide with or may be set lower than a lower end of the light guide passage.
A top of the first reflector may be formed of convex protruding inside of the first reflector to reflect upward light reflected from the first reflector as a horizontal light or downward light.
The inside of the light guide passage may be treated by reflection treatment or may be filled with a light guide material.
Further, the first reflector may be a parabolic free curved surface and the third reflector may have a width at the front side of the light source wider than that at the back side of the light source.
A further object of the present invention is to provide a headlamp for vehicle, being capable of providing appropriate luminous intensity distribution properties for running and for passing-by.
The above-mentioned object of the present invention can be achieved by providing the following headlamp for a vehicle.
Namely, the present invention provides a headlamp for a vehicle, comprising: a light source; a first reflector formed of a parabolic reflector which is cut at upper arid lower portions thereof and having a focal point at which the light source is positioned, an optical. axis thereof being directed to an illuminating direction; a pair of second reflectors each formed of an elliptic type reflector provided above the first reflector so as that the major axis thereof is perpendicular to the optical axis in a horizontal direction, and having a first focal point at which the light source is positioned; a pair of third reflectors each formed of a parabolic reflector having a focal point at which a second focal point of each of the second reflectors is positioned, and provided at the both outsides of the first reflector; and a fourth reflector formed of a parabolic reflector having a focal point at which the light source is positioned, an optical axis thereof being directed to the illuminating direction, and provided below the first reflector.
According to the headlamp for vehicle of the present invention having the above-mentioned configuration, it becomes possible to provide appropriate luminous intensity distribution properties for running and for passing-by and resolve the problems in the prior art lamps which deteriorate the vehicle performances, and also to improve the performances of the vehicle headlamp.
In addition, it is possible to provide an original design of a headlamp when installing the headlamp into a vehicle to improve an original appearance and commercial value. Furthermore, luminous flux efficiency of the headlamp can be improved by removing the necessity of a hood or stripe to provide a brighter headlamp and to improve commercial value thereof.
In the above-mentioned headlamp for a vehicle, there may be further provided with a pair of first mirrors having their reflecting surfaces directing upward along the major axes of the second reflectors, respectively and provided in such a manner that tip ends thereof coincide with the second focal points of the second reflectors, respectively, and a pair of third mirrors having their reflecting surfaces directing to the light source side and provided at both sides of the light source, wherein one of the pair of first mirrors or the pair of third mirrors is movable in the vertical direction to change luminous intensity distribution.
Further, the tip ends of the pair of first mirrors may be asymmetric in an angle when intersecting with the major axis of the second reflector.
In addition, the tip ends of the pair of first mirrors may be perpendicular to the major axis, and the first mirrors may be tilted in an appropriate angle relative to the major axis as a rotation axis.
Furthermore, a border between light and shade of the luminous intensity distribution for passing-by may be formed by the tip ends of the first mirrors.
One of the tip ends of the first mirrors may form an elbow portion of the border between light and shade in the luminous intensity distribution for passing-by, and the other of the tip ends of the first mirrors may form a horizontal portion of the border between light and shade in the luminous intensity distribution for passing-by.
Further, a second mirror may be provided so as to direct a reflecting surface thereof to the first mirrors. Still further, the second mirror may be provided so as to receive a reflected light from the first mirror.
In addition, the first and second mirrors may be formed integrally.
Further, both the first and third mirrors may be moved in the same direction of either upper or lower direction to change the luminous intensity distribution.
In the above case, movement of the first mirrors may be simultaneously carried out with the movement of the third mirrors.
Furthermore, the third mirrors may preferably be inclined to shorten the distance between the upper ends thereof and widen the distance between the lower ends thereof.
In addition, the third mirrors may not have a reflecting function.
Furthermore, at least one of the first, second and third mirrors may be formed of a curved surface.
Alternatively, at least one of the first and third mirrors may be formed of a free curved surface.